This study marks the first application of Acceptance and Commitment Therapy (ACT) to the treatment of a university student with music performance anxiety (MPA). ACT is a newer, "third-wave" therapy that differs from previous MPA treatments, because its goal is not to reduce symptoms of MPA. Rather, ACT aims to enhance psychological flexibility in the presence of unwanted symptoms through the promotion of six core processes collectively known as the ACT "hexaflex." For this study, an undergraduate violinist with debilitating MPA received a 10-session ACT treatment using a single-subject design. Treatment consisted of an orientation to ACT, identification of experientially avoidant behaviors, facilitation of hexaflex processes, in-session performances in which valued behaviors were practiced, meditations, homework, and regular completion of ACT-based and symptom-based measures. Clinically significant improvements were observed in her ability to accept and defuse from her anxious thoughts and feelings at post-treatment and at a 1-month follow-up. Her performance quality also improved at post-treatment. Although symptom reduction was not a goal, her MPA and overall distress were significantly reduced, and her perceived control over MPA significantly improved at post-treatment and follow-up. These results suggest ACT may be an effective treatment option for MPA and should be studied further.